Ti掺杂Nd_(2)Fe_(14)B/α-Fe纳米双相复合永磁体晶化动力学

Crystallization kinetics of Ti-doped Nd_(2)Fe_(14)B/α-Fe nanocomposite permanent magnets

纳米双相复合稀土永磁材料,利用硬磁相高磁晶各向异性和软磁相高饱和磁化强度的优点,通过铁磁交换耦合作用获得优异的磁性能.但是如何解决软硬磁双相纳米微结构不匹配的问题,控制软硬磁相同时达到理想的纳米尺度复合是关键.本文研究了掺杂合金元素Ti对熔体快淬法制备的Nd_(2)Fe_(14)B/α-Fe快淬薄带晶化过程的影响.结果表明,掺杂合金元素Ti能影响Nd_(2)Fe_(14)B/α-Fe交换耦合磁体整个晶化动力学过程,使α-Fe相的晶化激活能升高,抑制其从非晶相中析出.同时,降低1∶7亚稳相的晶化激活能,起到稳定亚稳相的作用.而且随着晶化温度的进一步提高,α-Fe和Nd_(2)Fe_(14)B两相由1∶7亚稳相分解产生,从而有效避免了α-Fe相的优先析出.显微组织观察表明,掺杂Ti的样品晶粒细小、分布均匀,平均晶粒尺寸在20 nm左右,没有特别大的α-Fe粒子出现.当Ti的掺杂量原子百分数为1.0%时,获得了最佳磁性能(BH)_(max)=12 MG·Oe(1 G=10^(-4)T,1 Oe=79.57795 A/m).

Nanocomposite magnet consisting of a fine mixture of magnetically hard and soft phase has received much attention for potential permanent magnet development.One of the important requirements for alloys to exhibit excellent magnetic properties is a nanocrystalline grain size.The soft and hard magnetic phases can simultaneously achieve ideal nanoscale composites.The effect of Ti additions in the amorphous crystallization process of the exchange-coupled nanocomposite Nd_(2)Fe_(14)B/α-Fe magnet prepared by melt spinning is investigated.The results show that Ti can change the crystallization kinetics of the NdFeB melt-spun ribbons.The Ti can increase the activation energy ofα-Fe and contrarily reduce the activation energy of a metastable 1∶7 phase,so the growth speed ofα-Fe decreases and the metastable 1∶7 phase can stably precipitate from the amorphous phase.When the annealing temperature increases,a metastable 1∶7 phase is decomposed into theα-Fe phase and the Nd_(2)Fe_(14)B phase.The microstructure observation shows that the grains of the alloys doped with Ti are fine and uniform,with an average grain size of about 20 nm,and no particularly largeα-Fe particles appear.The optimal magnetic property is(BH)_(max)=12 MG·Oe(1 G=10^(-4)T,1 Oe=79.57795 A/m)when Ti addition is 1.0%.